If you are amazon prime member, it’s usually FREE when you return your orders. But you will charged if you choose, “Better price available”, that is the ONLY ONE reason you will be charged for return shipping fee.
If you are choosing the “no longer needed” or “bought by mistake” option, Then You will be charged for return shipping. But You can choose other option except “no longer needed” or “bought by mistake ” options, You will not be charged for shipping.
See screenshot photo for details:

Anyways, even if you are charged, you can show your prove of payment(just a screenshot of the email) and ask them to refund using online chat with the amazon associates. It’s quick and easy.

They first offer is just a $10 gift card(But I paid for $10.47). No. I don’t want to buy on amazon if it’s not necessary.
So simply tell them to return the money to your bank. I hope you won’t be charged for returns as a prime membership owner, and also not refund for LESS than what you paid.